Process for removing tannic acid from coconut fibers with sodium hydrosulphite and then bleaching the fibers



United States Patent PROCESS FOR REMOVING TANNIC ACID FROM COCONUT FIBERS WITH SODIUM HYDROSUL- PHITE AND THEN BLEACHING THE FIBERS Johannes Margarethus Bulder, Amsterdam, Netherlands, assignor to N. V. Amsterdamsche Maatschappij Tot Exploitatie Van Octrooien, Amsterdam, Netherlands, a limited-liability company of the Netherlands No Drawing. Application June 22, 1953 Serial No. 363,407

2 Claims. (Cl. 8-108) The present invention relates to a process for the bleaching of coconut fibres.

It is known to bleach vegetable fibres by treating them with a warm solution of sodium hydrosulphite and thereupon with solutions containing active chlorine.

The great difiiculty when producing coconut fibres either by hand or by machinery is the maintaining of the original color. The coconut fibres are rather white by nature. They contain tannic acid, however, which on exposition of the fibres to the air is oxidized to phlobaphenes. This chemical reaction changes the color of the fibres from white to brown or black and makes them become hard and stifi. The phlobaphene once formed can never be removed completely from the fibres.

The process according to the invention aims at preventing the oxidation of the tannic acid and the removal of the tannic acid by treating the coconut fibres immediately after having been freed from the surrounding husk with a warm solution in water of sodium hydrosulphite (Na S 0 The percentage of hydrosulphite depends on the length of time that the husks have been stored.

Coconut fibres bleached by this treatment can be dyed in lighter colors than heretofore possible.

Coconut fibre treated by the present process is a nearly 100% white durable material.

When the aforementioned bleached material is treated with chlorite-containing bleaching baths a pure white fibre is obtained.

Example Immediately after separation from the pitch or cofferdam coconut fibres are treated for a duration of minutes with a 1 to 2% solution of sodium hydrosulphite, at a temperature of 70-90 C. Thereupon the fibres are washed with water and dried. Coconut fibres it cilia w. 1

are obtained as white as sisal, said fibres maintaining this color for a long period of time.

If further bleaching is desired, the fibres are treated at -80 C. with a solution in water of chlorous acid, containing 4 g. of C10,; per liter. The fibres are then rinsed in water. The bleaching and rinsing steps may be repeated if the fibres have not been bleached to the required degree of whiteness.

What I claim is:

1. A process for preventing oxidation of freshly liberated coconut fibers, comprising the steps of separating the fibers from the husks of coconuts and immediately impregnating the fibers before the same have become oxidizedand discolored with a tannin extracting aqueous solution of 2% sodium hydrosulphite at a tem perature between 70 and C. for at least 15 minutes, washing the fibers with water and finally allowing them to dry, whereby the fibers are prevented from being discolored through oxidation upon exposure of said fibers to the atmosphere.

2. A process for preventing oxidation of freshly liberated coconut fibers, comprising the steps of separating the fibers from the husks of coconuts, immediately impregnating the fibers before the same have become oxidized and discolored with a tannin extracting aqueous solution of 2% sodium hydrosulphite at a temperature between 70 and 90 C. for at least 15 minutes, bleaching said fibers by applying to said fibers an oxidative aqueous bleaching solution of chlorous acid, washing said fibers with water and finally drying said fibers, whereby the fibers will be prevented from being discolored through oxidation of the tannic acid therein upon exposure of said fibers to the atmosphere.

References Cited in the file of this patent UNITED STATES PATENTS 1,027,953 Wickham May 28, 1912 1,912,345 Del Plaine May 30, 1933 1,965,061 Turnbull July 3, 1934 2,030,384 Luth Feb. 11, 1936 2,372,561 Elgi'n Mar. 27, 1945 FOREIGN PATENTS 726 Great Britain 1860 13,753 Great Britain 1913 OTHER REFERENCES Matthews: Textile Fibers," fifth ed., John Wiley 8: Sons, New York, 1947, pages 415-418. 

2. A PROCESS FOR PREVENTING OXIDATION OF FRESHLY LIBERATED COCONUT FIBERS, COMPRISING THE STEPS OF SEPARATING THE FIBERS FROM THE HUSKS OF COCONUTS, IMMEDIATELY IMPREGNATING THE FIBERS BEFORE THE SAME HAVE BECOME OXIDIZED AND DISCOLORED WITH A TANNIN EXTRACTING AQUEOUS SOLUTION OF 2% SODIUM HYDROSULPHITE AT A TEMPERATURE BETWEEN 70* AND 90*C. FOR AT LEAST 15 MINUTES, BLEACHING SAID FIBERS BY APPLYING TO SAID FIBERS AN OXIDATIVE AQUEOUS BLEACHING SOLUTION OF CHLOROUS ACID, WASHING SAID FIBERS WITH WATER AND FINALLY DRYING SAID FIBERS, WHEREBY THE FIBERS WILL BE PREVENTED FROM BEING DISCOLORED THROUGH OXIDATION OF THE TANNIC ACID THEREIN UPON EXPOSURES OF SAID FIBERS TO THE ATMOSPHERE. 